The present invention relates to the arrangement of the shock absorbing structure of a bicycle, and relates more particularly to such a bicycle shock absorbing arrangement which constantly keeps the chain and the chain wheel in positive engagement.
FIG. 1 shows a conventional bicycle shock absorbing system in which the rear ends of the chain stays 11a and the seat stays 12a are respectively connected together and pivoted to the rear hub sprocket 16a; the front end of the chain stays 11a is pivoted to a pivot A at a pivot holder 13a; the front end of the seat stays 12a is supported on a shock absorbing spring 10a at the seat tube of the bicycle. When the rear wheel 14a runs over an uneven road, the chain stays 11a is forced by the rear wheel 14a to turn about the pivot A, and the seat stays 12a is forced to act against the shock absorbing spring 10a, causing the shock absorbing spring 10a to absorb shock waves. This shock absorbing structure is still not satisfactory in function. Because the pivot A and the bottom bracket bearing axle B of the chain wheel 15a are disposed at different locations, the chain stays 11a is turned about the pivot A but not about the bottom bracket bearing axle B when the rear wheel 14a runs over an uneven road, thereby sing the distance between the chain wheel 15a and the rear hub sprocket 16a to be changed. When the distance between the chain wheel 15a and the rear hub sprocket 16a is changed, the tension of the chain 17a will be relatively changed, causing a transmission error. Furthermore, because the pivot holder 13a support the chain stays 11a, it tends to be damaged when the chain stays 11a is forced to vibrate.